Crash when formatting case and macro for

[wooster0]

case
{% for index in 0..0 %}
{% end %}
end

$ crystal tool format --show-backtrace

expecting {%, not `NEWLINE, `, at :1:5 (Exception)
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???
  from ???

couldn't format './cr.cr', please report a bug including the contents of it: https://github.com/crystal-lang/crystal/issues

[jan-zajic]

It is not a valid macro, you can't do that. As documented here: Macros

This means, for example, a macro cannot generate a one or more when expressions of a case statement unless case was a part of the generated code.

You can do this:

{% begin %}
case
{% for index in 0..0 %}
{% end %}
end
{% end %}

[straight-shoota]

Technically, the code is valid because the expanded macro is empty. But of course, it doesn't make sense because you can't do anything useful with it.

Still, since it's valid syntax, the formatter should be able to handle it.

We could also consider making an outer macro expansion directly following a case or when expression a syntax error.

[asterite]

Also this fails to format:

case
1
end

The above is equivalent to:

case 1
end

In the original snippet it's the same.

I wonder if we should disallow the condition case condition to be in a separate line... it looks pretty weird. Same goes for if, while, etc. 🤔

[straight-shoota]

@asterite I would have never assumed that a newline would be appropriate at the location. So 👍

Especially for case, which can go without an expression, it looks confusing.

[straight-shoota]

So only use case I could think of is when the expression is very long and you want to split it into serveral lines, it makes sense to start all lines at the same column. But the formatter already takes care of that, at least for if and unless:

if a_long_conditional_expression &&
   another_even_longer_expression &&
   this_is_the_longest_expression_of_them_all
  body
end
unless a_long_conditional_expression &&
       another_even_longer_expression &&
       this_is_the_longest_expression_of_them_all
  body
end

But not with case:

case a_long_conditional_expression &&
  another_even_longer_expression &&
  this_is_the_longest_expression_of_them_all
when foo
  body
end